The White River and Northern Model Railroad: Clinic

	The N Scale

	Model Railroad

The Village Vidiot

The Village Vidiot video store

How many times have we seen model chaser light signs? Fairly often, as they are available in kits and occasionally built from scratch. Typically the chaser lights themselves are fiber optics, which are bundled together into three groups and illuminated sequentially by a trio of electrically-controlled LEDs.

The sign I made for the "Village Vidiot" video store, I suspect, is unique. I'm something of a purist when it comes to lighting and animation effects, and while I might have been able to make use of a stock chaser light illumination unit, I'm not fond of the effect of blinking LEDs: they flash on and off instantaneously, and in real life chaser lights are brilliant incandescent lamps that have a perceptible period of brightening and, in particular, dimming; the best effect is a softer, more fluid lighting sequence. I also wanted the color temperature of tungsten lights, which is tough to accomplish with LEDs. And finally, the sign had to be considerably smaller than most typical chaser light signs, so there was no off-the-shelf product to suit my needs.

My idea: create a mechanical device that rotates a set of bulbs across the ends of the fibers. My challenge: a finished sign measuring 1/4-inch high by 1/2-inch wide, with no option of placing the device under the building. My solution: a miniature mechanism utilizing microbulbs in a drum rotated by a geared micromotor. It turned out to be one of the most intricate little mechanisms I'd ever built, with an overall size of 0.5 inches wide by 1.5 inches high by 1.5 inches deep. OK, so I'm really the village vidiot.

For masochistic readers, here is a detailed account of the mechanism's construction. The illustration below gives you an idea of the device's complexity, so you may or may not wish to proceed through the entire description that follows...

The 1/4- by 1/2-inch sign graphic was created on a PC using CorelDraw and printed on white self-adhesive label stock in a laser printer. The design included white dots in the black chaser light border to help guide drilling for the fiber optics. After applying the label to a piece of clear styrene sheet (a scrap of structure kit window glazing), I cut the styrene to match the size of the sign and then began the tedious task of carefully drilling 30 holes for the fibers. I chamfered the holes slightly so that the flared ends of the fibers would fit flush with the sign face, then painted the edges of the sign with flat black paint.

The center of the sign is illuminated with two microbulbs enclosed within a light chamber. The chamber was created by bending a thin strip of sheet brass into a rectangle that fit within the fiber optic holes. A piece of 1/8-inch thick styrene was cut to match the rectangle and tapered to clear the fibers as they bundle together. The block was also drilled to accept the microbulb wires as well as two 1/16-inch brass rod electrical connection/mounting pins. After installing the two bulbs and connecting them to the mounting pins, the chamber was assembled with CA and glued to the back of the sign.

A piece of .020 sheet brass was cut to match the back of the light chamber, with the edges filed to match the taper of the styrene block. This part serves as the mounting plate for the fiber optic positioning assembly as well as one of two drum needle bearings, both of which are created using telescopic tubing. It is easier to show how this assembly was constructed than describe it, so refer to the cross-section below for the parts involved (bear in mind the long dimension is 1.5 inches):

The innermost part is a piece of rod stock drilled endwise to create a needle bearing dimple. This and the next two sections of tubing were soldered together, filed flat, and soldered to the plate that was cut to fit the back of the light chamber. This assembly was bonded to the light chamber styrene block with CA.

Next, 30 lengths of fiber optic material were cut slightly longer than needed; one end of each was flared by placing it near a hot soldering iron tip, then inserted into the sign from the front. The next piece of brass tubing (which was chamfered and buffed with a fine wire brush to prevent scratching the fiber optics) was slid over the fibers and into position. The fibers were trimmed flush with the brass tubing, and then a short bit of large styrene tubing (which prevents light from leaking past the drum toward the viewer) was cemented in place to complete the fiber optic assembly.

The last big challenge was creating the light drum. It consists of two brass discs measuring roughly 1/4-inch in diameter and a 1/4-inch thick block of styrene cut to match. The styrene part and one brass disc were drilled with six holes to accept microbulbs; the other brass disc was drilled with tapered holes to form light apertures. Two lengths of 1/8-inch brass rods were each mounted in a drill chuck and ground down with a file to form points; then they were soldered in holes in the center of the brass discs, and everything was sandwiched together with CA. Six microbulbs were fitted into the drum and their leads were carefully soldered to the edges of the brass discs. Finally, from the junk box I rescued a crown gear from an old slot car mechanism; I drilled it out to press-fit onto the longer drum shaft.

The mechanism in black. Two more parts left to fabricate. One was the main mounting plate, which was a rectangle (actually a trapezoid, since the end of the building was not square—see the photo of the finished, installed mechanism at right) cut from 1/8-inch thick styrene. It was drilled to accept the two mounting pins at the front of the mechanism, the geared micromotor adjacent to the crown gear, and two screws to mount it to the structure wall. The sign mounting pins were press-fit into holes in the mounting plate and secured with CA.

The last part was the combination needle bearing/electrical contact, made from a scrap of thin phosphor bronze. Before bending it into the final L-shape, I drilled one end for a mounting screw, and used a tiny nail and a hammer to form the needle bearing dimple in the other end. With the sign mechanism mounted to the main mounting plate, I was able to determine exactly where the bend needed to be for the phosphor bronze spring part to properly align the drum assembly. The spring had to be adjusted such that it applied enough pressure to hold the drum in place and provide good electrical contact, but not so much pressure that it caused the drum to jam. With the spring temporarily clamped to the mounting plate, I ensured the drum could spin easily before drilling and tapping the mounting plate for the spring part mounting screw.

The micromotor was attached, and the crown gear was adjusted to properly engage the motor pinion gear by sliding it down the shaft. By happy accident, the right rate of speed for the chaser lights was achieved with a 1.5-volt supply for the micromotor, which meant that all of the lights and the motor could be powered by the same source: a D-cell battery.

After all of that work, the building that housed the Village Vidiot wound up located at the back of the WR&N IV! While the layout no longer exists, the Village Vidiot was saved and can be seen on Rick Spano's Sceniced and Undecided, where it belongs—at the front of the layout. By the way, the video store resides in one half of a building that also features the barber shop with working barber pole, another dynamic lighting effect accomplished with a micro-mechanism.

Image specs: These images were captured with a Canon 20D digital SLR and a 50mm prime lens with a 12mm extension tube. Since the floodlight used to illuminate the building washed out the sign lights, a separate exposure of the sign was digitally inserted into the scene. The sign exposure was quite long (~15 seconds) causing the otherwise flashing chaser lights to appear uniformly illuminated.

See the chaser lights in action! | Watch it on YouTube

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